1. Field of the Invention
The present invention relates to a system and method for analyzing the precision of geo-location services in a wireless network. Specifically, the system and method allows network infrastructure planners to determine the best physical locations of references when identifying the geographic location of mobile terminals in a wireless network and, in particular, a wireless ad-hoc network, to achieve accuracy requirements. The system and method includes a software and hardware application that provides planners interactive visual feedback in evaluating placements that optimize geo-location coverage while minimizing infrastructure requirements.
2. Description of the Related Art
Wireless communications networks, such as mobile wireless telephone networks, have become increasingly prevalent over the past decade. These wireless communications networks are commonly referred to as “cellular networks”, because the network infrastructure is arranged to divide the service area into a plurality of regions called “cells”. A terrestrial cellular network includes a plurality of interconnected base stations, or base nodes, that are distributed geographically at designated locations throughout the service area. Each base node includes one or more transceivers that are capable of transmitting and receiving electromagnetic signals, such as radio frequency (RF) communications signals, to and from mobile user nodes, such as wireless telephones, located within the coverage area. The communication signals include, for example, voice data that has been modulated according to a desired modulation technique and transmitted as data packets. As can be appreciated by one skilled in the art, network nodes transmit and receive data packet communications in a multiplexed format, such as time-division multiple access (TDMA) format, code-division multiple access (CDMA) format, or frequency-division multiple access (FDMA) format, which enables a single transceiver at the base node to communicate with several mobile nodes in its coverage area.
In recent years, a type of mobile communications network known as an “ad-hoc multi-hopping” network has been developed to address the needs of multiple mobile device communication beyond traditional infrastructure coverage. In this type of network, each user terminal (hereinafter “mobile node”) is capable of operating as a base station or router for other mobile nodes within the network, thus eliminating the need for a fixed infrastructure of base stations. Accordingly, data packets being sent from a source mobile node to a destination mobile node are typically routed through a number of intermediate mobile nodes before reaching the destination node.
More sophisticated ad-hoc networks are also being developed which, in addition to enabling mobile nodes to communicate with each other as in conventional ad-hoc multi-hopping networks, further enable the mobile nodes to access fixed networks and communicate with other types of user terminals, such as those on the public switched telephone network (PSTN) and the Internet. Details of these advanced types of ad-hoc networks are described in U.S. Pat. No. 7,072,650 entitled “Ad Hoc Peer-to-Peer Mobile Radio Access System Interfaced to the PSTN and Cellular Networks”, issued on Jul. 4, 2006, in U.S. Pat. No. 6,807,165 entitled “Time Division Protocol for an Ad-Hoc, Peer-to-Peer Radio Network Having Coordinating Channel Access to Shared Parallel Data Channels with Separate Reservation Channel”, issued on Oct. 19, 2004, and in U.S. Pat. No. 6,873,839 entitled “Prioritized-Routing for an Ad-Hoc, Peer-to-Peer, Mobile Radio Access System”, granted on Mar. 29, 2005, the entire content of each being incorporated herein by reference.
The mobile nodes of such networks may assume any number of random positions within the network, making exact node location determinations difficult at times. In either conventional wireless communications networks, or in ad-hoc wireless communications networks, it may be necessary or desirable for a mobile node to be capable of knowing or determining its geographic location. Different types of location determining services and techniques for wireless communications networks are described in a publication by Nokia which can be found on the Nokia website at “www.nokia.com/press/background/pdf/mlbs.pdf”, the entire contents of which being incorporated herein by reference. Further details of location determining services and techniques for wireless communications networks are described in a Nokia White Paper entitled “Mobile Location Services”, the entire content of which being incorporated herein by reference.
In particular, the Nokia document states that location identification services are currently provided in wireless communications networks based on three major technologies. One of these technologies uses cell identification combined with Round Trip Time (RTT), sometimes called Time Of Flight (TOF), Timing Advance (TA) and Measured Signal level (RX level), Time Difference of Arrival (TDOA) and Angle Of Arrival (AOA) techniques, the details of which can be appreciated by one skilled in the art. A second technology uses cellular signal timing based methods for code division multiple access (CDMA) and wideband code division multiple access (WCDMA). The third technology described in the Nokia document employs Global Positioning System (GPS) techniques.
Another list of methods and techniques currently used in the wireless communications industry for providing location services is presented in an article by DISPATCH Monthly entitled “E911 Location Technologies”, the entire content of which is incorporated herein by reference. Although the GPS technique is the last technique mentioned in this list, it generally is viewed as being more accurate than all other methods listed. Further details and descriptions of GPS based methods are set forth in a publication by J. J. Spilker Jr. entitled “Satellite Constellation and Geometric Dilution of Precision” in “GPS—Theory and Applications”, American Institute of Astronautics, Inc., 1996, also in a publication by P. Axelrad et al. entitled “GPS Navigation Algorithms” in “GPS—Theory and Applications”, American Institute of Astronautics, Inc., 1996, also in a publication by Bradford W. Parkinson entitled “GPS Error Analysis” in “GPS—Theory and Applications”, American Institute of Astronautics, 1996, and in a publication by N. Ashby et al. Entitled “Introduction to Relativistic Effects on the Global Positioning System” in “GPS—Theory and Applications”, American Institute of Astronautics, 1996, the entire contents of each of these publications being incorporated herein by reference.
However, most methods and techniques described above can be improved if references used in providing location services are positioned in optimum physical or geographical locations throughout the network. Accordingly, a need exists for a system and method for assisting network infrastructure planners to determine the best physical locations of references when identifying the geographic location of mobile terminals in a wireless network.